Connect LoPy LoRa with Semtech Board

I am trying to connect Semtech LoRa development board with LoPy. I am sending 9 bytes of payload from Semtech board each 2 seconds. Format of the packet that is sent from Semtech board is: first 4 bytes are unsigned int (used for packet ID), other 5 bytes are dummy.

I am able to receive packets on LoPy, but with following problems:

Not able to receive each packet, but every second (packet loss is 50%)

Able to extract packet ID properly only if reading first two bytes: _LORA_PKG_FORMAT = "H" (unsigned short int, 2 bytes). If I put _LORA_PKG_FORMAT = "I" (unsigned int, 4 bytes), it is decoded as garbage.